U.S. Pat. No. 6,737,809 concerns a dielectric waveguide integrated plasma lamp (DWIPL) with a body consisting essentially of at least one dielectric material having a dielectric constant greater than approximately 2, and having a shape and dimensions such that the body resonates in at least one resonant mode when microwave energy of an appropriate frequency is coupled into the body. A bulb positioned in a cavity within the body contains a gas-fill which when receiving energy from the resonating body fauns a light-emitting plasma.
WO 2007/079496 concerns an electrode less plasma lamp comprising a lamp body including a solid dielectric material. The lamp includes a bulb received at least partially within an opening in the solid dielectric material and a radio frequency (RF) feed configured to provide power to the solid dielectric material. A conductive material is provided adjacent to the bulb to concentrate the power proximate the bulb. The conductive material may be located below an upper surface of the solid dielectric material. The conductive material may modify at least a portion of an electric field proximate the bulb so that the portion of the electric field is oriented substantially parallel to an upper surface of the lamp body.
There are several issuers related to the prior art electrodeless plasma sources (ELPS) such as those disclosed in U.S. Pat. No. 6,737,809 and WO 2007/079496. The ELSP bulb is positioned in an ELSPS resonator and the gas-fill inside the ELPS bulbs are exited by electromagnetic radiation in the microwave frequency. Some of the electromagnetic radiation used to excite the gas-fill, escapes the resonator which in many cases is unwanted electromagnetic interference with the surroundings. The electromagnetic radiations will especially escape through the ELSP bulb together with the light. Another issue is the fact that the ELPS bulb tends to flicker and changes it optical spectrum if not cooled properly. The lift time of the electrodeless plasma source is further shortened if the bulb is not sufficiently cooled. Yet another issue is the fact that the color temperature of the light from the ELSP tends to drift when the ELSP is dimmed. The ELPS is as a consequence very difficult to integrate in to complex optical systems like the ones used in entertainment lighting, such as moving heads and scanners, and in video projection systems.